1. Field of the Invention
The present invention relates to the domains of optical spectroscopy and cellular phones or other portable electronic devices. In one particular aspect, this invention relates to spectrometers miniaturized for working with cellular phones and other portable electronic devices. In another particular aspect, this invention relates to a cellular phone or other portable electronic device that has a miniaturized spectrometer being built-in or attached.
2. Description of the Related Prior Art, Compact Spectrometers
Instruments used for spectroscopic measurements and applications belong to one family of spectrometers. A spectrometer is an optical instrument for measuring and examining the spectral characteristics of the input light over some portion of the electromagnetic spectrum, where the measured variable is often the light intensity.
A typical optical system of a spectrometer basically comprises an element(s) for collimating, an element(s) for dispersing and an element(s) for focusing to form spectral images. The entrance slit of a spectrometer functions as the input interface, where an optional input optics exists, and divergent input optical beams are fed into the spectrometer. In order to maximize the throughput efficiency, apertures of all optical elements within the spectrometer have to be large enough to accept full optical beams without truncation, which in return, leads to a three-dimensional propagation path. Its detector, usually a (linear) CCD mounted at its spectral image plane, converts optical signals to electronic signals, allowing an instant full spectrum of the input light being acquired since a spectrometer does not have a moving parts for scanning. All of these make a spectrometer, as a useful spectroscopic instrument, cumbersome (i.e. complex in construction), large in body volume and heavy in weight. Moreover, there exist a couple of technical problems inherently associated with this kind of spectrometer: astigmatism over the spectrum on the detector plane, and field curvature from the spectrum focused onto the detector plane, as reviewed by U.S. Pat. No. 5,880,834 (1999) to Chrisp.
As a result, it has become challenge to design and build a spectrometer with innovative features to overcome the drawbacks and technical problems identified above, to which, substantial efforts have been directed and numerous improvements have been published for the purposes of simplifying its optics, minimizing its body volume, reducing its weight, and eliminating optical aberrations, mainly astigmatism and field curvature. Among those areas of concerns, constructing compact spectrometers has generated manifold attentions since the trend in modern spectrometer systems is towards a compact one. A compact spectrometer has the potential to open up for more applications in many industries, as discussed below.
Representatives of the art can be categorized in accordance with their construction features associated with compact spectrometers: spectrometers of simple optics, spectrometers of a monolithic career body, and spectrometer constructed with a waveguide substrate.
A representative of the art for spectrometers of simple optics is U.S. Pat. No. 4,568,187 (1986) to Kita et la, which discloses a compact spectrometer comprising a single concave grating. The concave grating is manufactured with curved grooves of varied spacing for optimum performance, and functions for both dispersing and imaging. It has become a known art that a concave grating sets the minimum number of optical elements needed in a spectrometer, leading to a simplest structure form.
Another representative of the art for spectrometers of simple optics is U.S. Pat. No. 6,606,156 (2003) to Ehbets et la., which discloses a compact spectrometer comprising a concave grating, mounted on one side of the housing. The input port and the detector array are positioned opposite the concave grating, leaving a hollow cavity where the input optical beams propagate.
Another representative of the art for spectrometers of simple optics is U.S. Pat. No. 7,081,955 (2006) to Teichmann et la, which discloses a compact spectrometer comprising two parts: the main body with grating and the focusing element being formed on the top of the housing, and the bottom substrate of detector array with light entrance means. The integrated spectrometer has a hollow cavity where the input optical beams propagate.
Other representatives of the art for spectrometers of simple optics are U.S. Pat. No. 5,424,826 (1995) to Kinney, which discloses an optical micro-spectrometer system, and U.S. Pat. No. 5,550,375 (1996) to Peters et la, which discloses a compact spectrometer designed as infrared spectrometric sensor. Features in common for these two disclosures are that they are constructed for specific applications.
Among the representatives of the art for spectrometers of simple optics, one that has to be referenced is the Japanese Patent Application Publication JP 55-093030 A (1980) to Hasumi Ritsuo, which discloses a cylindrical-lens type spectrometer. Features for this publicized disclosure are that individual cylindrical lenses are used, which manipulate light beams in the vertical and horizontal directions separately, to construct a spectrometer with a compact volume profile.
A representative of the art for spectrometers of a monolithic career body is U.S. Pat. No. 5,026,160 (1991) to Dorain et la, which discloses a such solid monolithic spectrometer that utilizes the Czerny-Turner configuration on a base constructed of BK7 optical glass, to which all components are affixed with optical epoxy, leading to a compact spectrometer with a robust body of thick slab form. Its light entrance means and light detecting means are both placed on the same side of the spectrometer. Another representative of the art for a spectrometer built in a similar approach is disclosed in U.S. Pat. No. 5,754,290 (1998) to Rajic et la, which has an appearance of a solid, rectangular, three-dimensional body of translucent material with defined surfaces.
Another representative of the art for spectrometers of a monolithic career body is U.S. Pat. No. 5,159,404 (1992) to Bittner, which discloses a spectrometer where the concave grating and focusing mirror are combined together on one side of a single glass carrier, and the light entrance means and light detecting means are both placed on the other side of the spectrometer, resulting in a compact spectrometer with a robust body of spherical form.
Another representative of the art for spectrometers of a monolithic career body is U.S. Pat. No. 6,081,331 (2000) to Teichmann, which discloses a spectrometer that utilizes the Fastie-Ebert geometry on a cylinder body of glass, on which a concave mirror surface for collimating and focusing is formed at one end, the light entrance means and light detecting means, as well as the planar reflective grating, are placed on the other end of the career body.
A representative of the art for spectrometers constructed with a waveguide substrate is U.S. Pat. No. 4,744,618 (1988) to Mahlein, which discloses a device designed as multiplexer/demultiplexer for fiber communication systems. It is constructed on a very thin piece of solid monolithic glass. In principle, it works like a compact spectrometer since its input light propagates laterally along the Fastie-Ebert geometry. Meanwhile, its light propagation path is confined vertically based on total internal reflection between two interfaces of glass and the air. A waveguide substrate of sandwich structure is also reported as an alternative embodiment.
There exist a few other representatives of the art for spectrometers constructed with a waveguide substrate, including: U.S. Pat. No. 4,999,489 (1991) to Huggins, and U.S. Pat. No. 5,493,393 (1996) to Beranek et la for optical fiber application. Both of them disclose waveguide based WDM sensing systems. Their optics comprise a thin layer of waveguide as the light propagation media, and a single concave grating formed at the end of the device opposite to the input and output fiber ports.
Another representative of the art for spectrometers constructed with a waveguide substrate is U.S. Pat. No. 4,938,553 (1990) to Maerz et la, which discloses an integrated optical spectrometer having an arrangement of either a film waveguide plus a curved, ribbed waveguide, or only a film waveguide, wherein waveguide structure and ribbed grating are manufactured by etching. The dispersed spectral signals are preferably coupled into output fibers.
Another representative of the art for spectrometers constructed with a waveguide substrate is U.S. Pat. No. 5,812,262 (1998) to Ridyard et la, which discloses a spectrometer for UV radiation. Constructed by a single piece of waveguide carrier, its optics comprises a concave mirror and a reflective planar grating for focusing light from the entrance aperture means onto the radiation detector means. This configuration relies on a fixed order of the optical elements of focusing and then dispersing the light, which makes it difficult to compensate or avoid aberrations.
Another representative of the art for spectrometers constructed with a waveguide substrate is U.S. Pat. No. 7,034,935 (2006) to Kruzelecky, which discloses an infrared spectrometer comprising: a slab waveguide structure having a front input face, a rear concave face, and an output face, a diffraction grating provided on the rear concave face for diffracting the optical signal and directing spectral components onto the output face towards a detector array that is optically coupled to a slab waveguide structure.
As discussed above, most of the related art of compact spectrometers, including those classical spectrometers of simple optics and a monolithic career body, are still considered “cumbersome” and large in volumes for being integrated into a cellular phone to form a standalone system. Exceptions are: (1) the cylindrical-lens type spectrometer, and (2) waveguide based spectrometers, whose volumes are the smallest. Therein the volume difference is caused by the fact that a classical spectrometer is constructed with optical elements of finite two-dimensional apertures and has a light propagation path that is three-dimensional, leading to a larger three-dimensional volume, while in a cylindrical-lens type spectrometer light propagation paths are basically two-dimensional, and for a waveguide based spectrometer it is constructed from a thin monolithic glass substrate where exists a light propagation path in a thin layer (˜tens of micrometers) of glass media that are two-dimensional too, or unilateral. A cylindrical-lens type spectrometer or waveguide based technology may be utilized for integrating a compact spectrometer into a cellular phone or other portable electronic device.
However, in practice, there exist other issues that raise extra concerns in consideration of implementing those two candidate techniques. On one hand, a cylindrical-lens type spectrometer comprises more individual optical elements than its existing counterparts, leading to increases in both manufacturing cost and volume of the integrated package. On the other hand, the manufacturing process of waveguide products is expensive, and there are other technical concerned drawbacks associated with waveguide performance, including high propagation loss, stray light caused by scattering at waveguide boundary, etc. Besides, coupling efficiency of waveguide devices are very susceptible to misalignment at input ends. All of these factors have negative implications when considering whether to apply waveguide based spectrometers in more applications.
In general, existing spectrometers have not been an object of miniaturization as has been other technological machines and equipment because of the lack of technology in making it so. Thus, wider applications of spectrometers have not been possible for areas where miniaturization has become increasingly necessary or preferable. These disadvantages of existing spectrometers have been overcome with the present invention, both in the invention itself and the method with which it is made.
3. Description of the Related Prior Art, Cellular Phone
A cellular phone is a wireless and mobile phone. For the simplicity of discussion in the following sections, the term “cellular phone” and “mobile phone” are used equally in an exchangeable way. The earliest representative of the art of wireless telephone is U.S. Pat. No. 887,357 (1908) to Stubblefield, which discloses an invention applied to “cave radio” telephones between a vehicle to a vehicle, and a vehicle to a station. Since then, radiophones have gone through a long and varied history.
The introduction of cells for mobile phone base stations was invented in 1947 by Bell Labs engineers at AT&T. Memo by Douglas H. Ring proposing hexagonal cells, Nov. 11, 1947, Bell Telephone Laborlatries Incorporated. One of representatives for practically implementing cellular phone technology is U.S. Pat. No. 3,663,762 (1972) to Joel, Jr., which discloses an automatic “call handoff” system to allow mobile phones to move through several cell areas during a single conversation without loss of conversation. In general, Motorola is widely considered to be the inventor of the first practical mobile phone for handheld use in a non-vehicle setting. A representative of the art of cellular phone from Motorola is U.S. Pat. No. 3,906,166 (1975) to Cooper et la, a Motorola manager who made the first call on a handheld mobile phone on Apr. 3, 1973.
Other representatives of the art of historical significance include: U.S. Pat. No. 4,399,555 (1983) to MacDonald et la, U.S. Pat. No. 5,265,158 (1993) to Tattari, U.S. Pat. No. 5,722,067 (1998) to Fougnies, and U.S. Pat. No. 5,841,856 (1998) to Yoshiyuki Ide. Throughout the period covered by these representatives listed above, cellular phones are commercially introduced to civilians through three generations: 1G (1980˜1990) of an analog signal transmission technique supporting basic voice communication only, 2G (1990˜2000) of digital signal transmission technique, and 3G (2000˜2007) that offers increasing wideband transmission capability.
As technologies applied to cellular phone advance, more new features are being incorporated into cellular phones, resulting in new types of cellular phones being introduced with different names, like camera phones, PDA (personal digital assistant) phone or smartphone, and GPS phone, etc. . . . .
A camera phone is a mobile phone that has a camera built-in and is coupled with a server-based infrastructure or protocol, which allows the user to instantly share pictures and video with someone that has a device adapted to receive pictures and video. A representative of the art of camera phone is U.S. Pat. No. D405,457 (1999) to Kawashima, which discloses an ornamental design for a digital camera with cellular phone. Other typical representatives of the art of camera phone include: U.S. Pat. No. 6,823,198 (2004) to Kobayashi, U.S. Pat. No. 7,003,318 (2006) to Kota, et al, U.S. Pat. No. 7,117,011 (2006) to Makino, and U.S. Pat. No. 7,228,151 (2007) to Kota, et al, etc.
A PDA phone is a PDA and cell phone combination. PDA phones predominantly have data capabilities, multiple data input methods, wireless email functions, security and device management features, organizer functions, USB connection, charging from PC and extensive third party application support, supported by window based operating system. A smartphone on the other hand, is mainly a phone with some PDA phone features like organizer function, data viewing capabilities without editing functions. A representative of the art of PDA phone is U.S. Pat. No. D441,733 (2001) to Do, et al., which discloses a ornamental design for a multiple wireless PDA phone. There exist a few other representatives of the art of PDA phone, including U.S. Pat. No. D498,736 (2004) to Lee, U.S. Pat. No. D502,159 (2005) to Chan, et al., U.S. Pat. No. 7,043,284 (2006) to Tornaghi, U.S. Pat. No. D520,976 (2006) to LaDelfa, and U.S. Pat. No. D526,983 (2006) to Gong, et al.
Another representative of the art of cellular phone is: U.S. Pat. No. 6,993,573 (2006) Hunter, which discloses a camera cellular phone that is adapted to image a machine-readable code such as a bar code. It decodes the bar code and sends the bar code data over the Internet to a resolution server that will return an associated URL that will link the camera phone to content on an information server.
Another representative of the art of cellular phone is: U.S. Pat. No. 7,164,921 (2007) Owens, et al, which discloses a mobile phone having an internal GPS-receiver. It accommodates any applications in which a wireless communications device such as a cell phone can be caused to report location, with the phone initially in an off condition.
From above reviews of related prior art, it can be seen that a cellular phone has become so powerful that it have a numerous advanced capabilities, including: onboard CPU for data processing, LCD for real-time display, USB port for connection, operating system for supporting working environment, and the wireless communication capability to connect to other cellular phones or onto the internet. All of these considerations make a cellular phone an ideal platform for supporting real-time applications associated with a spectrometer.
On the other hand, it will not be physically possible to integrate a spectrometer into or with a cellular phone together, unless a spectrometer's size/volume is significantly reduced with a footprint compatible to that of a cellular phone. Thus, it is the intention of this invention to provide compact spectrometers miniaturized for working with cellular phones or other portable electronic device without scarifying their performances.